Allow AppEngineConnection to target services other than "tools"

This change required several things:
- Separating out the interfaces that merely do HTTP calls to the backend from those
  that require the remote API (only load the remote API for the latter).  Only the
  tools service provides the remote api endpoint.
- Removing the XSRF token as an authentication mechanism (with OAUTH, we no longer
  need this, and trying to provide it requires initialization of the datastore
  code which requires the remote API)

I can't think of a compelling unit test for this beyond what already exists.
Tested:
  Verified that:
  - nomulus tool commands (e.g. "list_tlds") work against the tools service as they
    currently do
  - The "curl" command hits endpoints on "tools" by default.
  - We can use --server to specify endpoints on the default service.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=211510454

java/google/registry/tools/RegistryCli.java

@@ -29,7 +29,6 @@ import com.beust.jcommander.ParametersDelegate;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Iterables;
 import google.registry.model.ofy.ObjectifyService;
-import google.registry.tools.Command.RemoteApiCommand;
 import google.registry.tools.params.ParameterFactory;
 import java.security.Security;
 import java.util.Map;
@@ -59,6 +58,8 @@ final class RegistryCli implements AutoCloseable, CommandRunner {
   @ParametersDelegate
   private LoggingParameters loggingParams = new LoggingParameters();
 
+  RegistryToolComponent component;
+
   // These are created lazily on first use.
   private AppEngineConnection connection;
   private RemoteApiInstaller installer;
@@ -76,6 +77,10 @@ final class RegistryCli implements AutoCloseable, CommandRunner {
     this.commands = commands;
 
     Security.addProvider(new BouncyCastleProvider());
+
+    component = DaggerRegistryToolComponent.builder()
+        .flagsModule(new AppEngineConnectionFlags.FlagsModule(appEngineConnectionFlags))
+        .build();
   }
 
   // The <? extends Class<? extends Command>> wildcard looks a little funny, but is needed so that
@@ -165,48 +170,43 @@ final class RegistryCli implements AutoCloseable, CommandRunner {
     }
   }
 
-  private void runCommand(Command command) throws Exception {
-    // Create the main component and use it to inject the command class.
-    RegistryToolComponent component = DaggerRegistryToolComponent.builder()
-        .flagsModule(new AppEngineConnectionFlags.FlagsModule(appEngineConnectionFlags))
-        .build();
-    injectReflectively(RegistryToolComponent.class, component, command);
-
-    if (!(command instanceof RemoteApiCommand)) {
-      // TODO(mmuller): this should be in the try/catch LoginRequiredException in case future
-      // commands use our credential.
-      command.run();
-      return;
-    }
-
+  private AppEngineConnection getConnection() {
     // Get the App Engine connection, advise the user if they are not currently logged in..
     if (connection == null) {
       connection = component.appEngineConnection();
     }
+    return connection;
+  }
 
-    if (command instanceof ServerSideCommand) {
-      ((ServerSideCommand) command).setConnection(connection);
+  private void runCommand(Command command) throws Exception {
+    injectReflectively(RegistryToolComponent.class, component, command);
+
+    if (command instanceof CommandWithConnection) {
+      ((CommandWithConnection) command).setConnection(getConnection());
     }
 
     // RemoteApiCommands need to have the remote api installed to work.
-    if (installer == null) {
-      installer = new RemoteApiInstaller();
-      RemoteApiOptions options = new RemoteApiOptions();
-      options.server(connection.getServer().getHost(), connection.getServer().getPort());
-      if (connection.isLocalhost()) {
-        // Use dev credentials for localhost.
-        options.useDevelopmentServerCredential();
-      } else {
-        options.useApplicationDefaultCredential();
+    if (command instanceof RemoteApiCommand) {
+      if (installer == null) {
+        installer = new RemoteApiInstaller();
+        RemoteApiOptions options = new RemoteApiOptions();
+        options.server(
+            getConnection().getServer().getHost(), getConnection().getServer().getPort());
+        if (getConnection().isLocalhost()) {
+          // Use dev credentials for localhost.
+          options.useDevelopmentServerCredential();
+        } else {
+          options.useApplicationDefaultCredential();
+        }
+        installer.install(options);
       }
-      installer.install(options);
-    }
 
-    // Ensure that all entity classes are loaded before command code runs.
-    ObjectifyService.initOfy();
-    // Make sure we start the command with a clean cache, so that any previous command won't
-    // interfere with this one.
-    ofy().clearSessionCache();
+      // Ensure that all entity classes are loaded before command code runs.
+      ObjectifyService.initOfy();
+      // Make sure we start the command with a clean cache, so that any previous command won't
+      // interfere with this one.
+      ofy().clearSessionCache();
+    }
 
     command.run();
   }